[GAP Forum] An overgroup of Sylow in PSL( 2, 7^3 )

[Anvita]

Dear Forum,

I need to construct a proper subgroup of PSL( 2, 7^3 ) that contains a
Sylow 2-subgroup.
According to the manual, IntermediateGroup returns `fail' if the subgroup
is maximal.
But the Sylow 2-subgroup is not maximal in this case.
Thank you in advance for any clarification.

Anvita

=====
gap> L := PSL(2,7^3);
<permutation group of size 20176632 with 2 generators>
gap>
gap> S := SylowSubgroup (L,2);
<permutation group of size 8 with 3 generators>
gap>
gap> U := IntermediateGroup(L,S);
fail
=====